Testis and epididymis
Germ cell tumors
Cystic trophoblastic tumor

Author: Vikas Mehta, M.D. (see Authors page)
Editoral Board Member Review: Debra Zynger, M.D.

Revised: 27 December 2017, last major update November 2017

Copyright: (c) 2017, PathologyOutlines.com, Inc.

PubMed Search: Cystic trophoblastic tumor full text[sb]

Cite this page: Mehta, V. Cystic trophoblastic tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/testisctt.html. Accessed July 21st, 2018.
Definition / general
  • Distinctive trophoblastic lesion secondary to either spontaneous or chemotherapy induced regression of choriocarcinoma
  • Described predominantly in postchemotherapy retroperitoneal lymph node dissections of patients with testicular germ cell tumors
  • Has also been described in both treated and untreated testes of patients with mixed germ cell tumors as well as in postchemotherapy primary central nervous system germ cell tumors
Essential features
  • Cystic proliferation of trophoblast cells in postchemotherapy resections from patients with metastatic, nonseminomatous germ cell tumors of the testis
  • Not aggressive with behavior believed to be similar to post-chemotherapy residual teratoma
Terminology
  • Cystic trophoblastic tumor (CTT)
  • Previously known as choriocarcinoma-like lesion (CCLL) with two subtypes: teratomatous CCLL and cystic atypical choriocarcinoma (Am J Surg Pathol 1988;12:531)
ICD-10 coding
Epidemiology
  • Typically seen in young males aged 16 - 40
Sites
  • Postchemotherapy retroperitoneal lymph nodes with mixed germ cell tumors
  • Treated or untreated testes with mixed germ cell tumors
  • Postchemotherapy primary central nervous system germ cell tumor
Etiology
  • May arise from regressing choriocarcinoma as the more aggressive cells are eliminated by chemotherapy or spontaneous regression, leading to the persistence of a slow growing, less aggressive component of intermediate type trophoblasts that develops into cystic trophoblastic tumor (Am J Surg Pathol 2017;41:788)
  • Cystic trophoblastic tumor may also represent an intermediate stage in the "maturation" of choriocarcinoma to teratoma (Am J Surg Pathol 2004;28:1212)
Clinical features
  • Most commonly seen in patients with testicular germ cell tumors after cisplatin based chemotherapy
Diagnosis
  • Histologic examination of involved tissue
Laboratory
  • Normal to mildly elevated levels of subunit of human chorionic gonadotropin (β hCG)
Radiology description
  • Enlarged retroperitoneal lymph nodes
Case reports
Treatment
  • Requires no further treatment, however these patients should be carefully monitored on follow up
Gross description
  • No grossly distinguishable features
Microscopic (histologic) description
  • Solid foci or small clusters of modestly pleomorphic trophoblastic cells and variably sized, degenerative appearing cysts, typically measuring less than 3 mm with circumscribed borders
  • Cysts are lined by trophoblast cells with abundant, eosinophilic cytoplasm that vary from a single cell layer to several in thickness, forming intracystic papillary tufts or cribriform arrangements
  • Most of the lining cells are mononucleated and many have a "smudged" chromatin pattern, although occasional multinucleated cells occur, sometimes with cytoplasmic lacunae
  • Many of the lining cells have a squamoid appearance, although no extracellular keratin production is apparent
  • Mitotic activity is inconspicuous, with only rare mitotic figures identified
Microscopic (histologic) images

Images hosted on PathOut server:

Images contributed by Dr. Vikas Mehta:

Large cyst in CTT

Intermediate type trophoblasts

Small cyst formation

β hCG

Positive stains
Negative stains
Differential diagnosis
Additional references
Board review question #1
Choriocarcinoma is distinguished from cystic trophoblastic tumor by all of the following features except:

  1. Biphasic pattern of admixed cytotrophoblast and syncytiotrophoblast cells
  2. Infiltrative growth pattern
  3. Normal to mildly elevated serum levels of β hCG
  4. Variable SALL4 expression in mononuclear cells
Board review answer #1
C. Normal to mildly elevated serum levels of β hCG
Board review question #2
Which of the following statements is true for cystic trophoblastic tumors (CTTs)?

  1. CTTs after chemotherapy show a high frequency of progressive disease and warrant additional chemotherapy
  2. CTTs are identified exclusively in the setting of postchemotherapy retroperitoneal lymph node dissections of patients with testicular germ cell tumors
  3. CTTs lack keratohyaline granules and central keratin, often have intracytoplasmic lacunae
  4. CTTs show goblet cells, ciliated cells and other specialized epithelial types
Board review answer #2
C. CTTs lack keratohyaline granules and central keratin, often have intracytoplasmic lacunae